Method and transmission apparatus for transmitting a bivalent signal

ABSTRACT

A method and an apparatus for transmitting information contained in a transmission signal via at least one channel includes a number of processing steps at the transmitter end. At least one pulse sequence with at least one pulse is produced as stipulated by the transmission signal. The pulse sequence is output to the at least one channel. The channel is monitored for the presence of an interference signal. If an interference signal is detected on the channel, the pulse sequence is repeated.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method and a transmissionapparatus for transmitting at least one signal via a channel, inparticular via a channel containing a potential barrier.

[0003] In electrical circuits, it is often necessary to transmitelectrical signals via a channel which contains a potential barrier inorder to isolate the potentials of a circuit which generates theelectrical signal and a circuit which receives the electrical signal oris actuated thereby. Examples of such circuits are signal transmittersin communications technology, DC-isolated transmission interfaces inindustrial electronics, or switched-mode converters in the form offlyback converters, for which a control signal dependent on the outputvoltage from the switched-mode converter needs to be transmitted to anactuating circuit actuating a switch. Another example are drivercircuits for power transistors, particularly for “high-side switches”,where control signals from a microcontroller, which normally havevoltage levels of 3.3 V or 5 V with respect to a reference-groundpotential, need to be transmitted to a driver circuit, which operate atmuch higher voltages or at a different reference-ground potential.

[0004] With methods for transmitting electrical signals via potentialbarriers, it is fundamentally known practice to transmit the signal fromthe transmitter end of the barrier to the receiver end of the potentialbarrier using capacitive, inductive or optical coupling methods.

[0005] The signal transmission via such potential barriers can bedisturbed from the outside, however. Thus, greatly variable electricalor magnetic fields can result in the signal to be transmitted beingdisturbed or corrupted, or in the channel becoming completely blocked ifan interference signal has such high power that the useful signal to betransmitted is completely extinguished.

[0006] If, by way of example, a bivalent signal is to be transmitted viasuch a potential barrier, then it is possible, as disclosed in U.S. Pat.No. 4,027,152, to convert the bivalent signal into a pulse sequence,with a positive pulse being transmitted if the level of the signal to betransmitted changes from a logic zero to a logic one and with a changein the level from a logic one to a logic zero entailing transmission ofa negative pulse. These positive or negative pulses are repeated orrefreshed at regular intervals of time, provided that the bivalentsignal does not change its level in the interim. If an interferencepulse means that “misinformation” is transmitted to the receiver in thecourse of these methods, then a correction is made upon the next refreshpulse.

[0007] Other methods in which a pulse or a pulse sequence is transmittedagain in order to avoid errors at the receiver end are known from U.S.Pat. Nos. 5,952,849 and 6,262,600 B1, for example. The method disclosedin U.S. Pat. No. 6,262,600 B1 for transmitting a bivalent signal via apotential barrier involves the generation of a cyclic signal whosefrequency assumes two different values on the basis of the present levelof the signal which is to be transmitted.

[0008] In the prior art methods, a pulse or pulse sequence generatedfrom the transmission signal which is to be transmitted is transmittedagain at regular intervals of time, regardless of whether interferenceis occurring on the transmission channel. This practice signifies a notinconsiderable involvement of energy, since energy is required for eachpulse sequence which is to be transmitted again or for each pulse whichis to be transmitted again. In addition, a signal with interference isfirst corrected by the next refresh pulse. In the worst case, the periodof time elapsing up to that point is equivalent to the period durationof the refresh pulses.

SUMMARY OF THE INVENTION

[0009] It is accordingly an object of the invention to provide a methodand an apparatus for transmitting a signal via a channel, whichovercomes the above-mentioned disadvantages of the heretofore-knowndevices and methods of this general type and which ensure a high levelof insensitivity to interference on the channel while reducing energyconsumption.

[0010] With the foregoing and other objects in view there is provided,in accordance with the invention, a method for transmitting informationcontained in a transmission signal via at least one channel. The novelmethod comprises the following steps, to be performed at a transmitterend:

[0011] generating at least one pulse sequence with at least one pulse asstipulated by the transmission signal;

[0012] outputting the pulse sequence to the at least one channel;

[0013] monitoring the channel for a presence of an interference signal;and

[0014] repeating the pulse sequence if an interference signal isdetected on the channel.

[0015] In other words, the method according to the invention fortransmitting information held in a transmission signal via at least onechannel makes provision, at the transmitter end, for at least one pulsesequence comprising at least one pulse to be generated as stipulated bythe transmission signal and for the pulse sequence to be output to theat least one channel. In addition, the channel is monitored for thepresence of an interference signal, and the pulse sequence istransmitted again if an interference signal is detected on the channel.

[0016] In the case of the inventive method, the pulse sequence dependenton the transmission signal is refreshed, that is to say isretransmitted, according to need only if interference is detected on thechannel. By contrast with known methods, this reduces the energyinvolvement of the inventive method. An interference pulse on thechannel can cause an error at the receiver end which is corrected againby virtue of the pulse sequence being transmitted again when aninterference pulse arises.

[0017] During interference signal detection, it is not possible todistinguish what is the cause of the interference on the channel. Theinventive method can thus also be used, in conjunction with a suitablereceiver, to use interference brought about by the receiver on thechannel to provoke a transmission pulse from the transmitter and henceto request the present transmitter state.

[0018] Preferably, following detection of the interference signal, theat least one pulse sequence is not transmitted until after theinterference signal has subsided, that is to say when no furtherinterference signal is detected.

[0019] In accordance with an added feature of the invention, thedetection of an interference signal before the pulse sequence dependenton the transmission signal has even been transmitted for the first timeentails the pulse sequence not being transmitted until after theinterference signal has subsided.

[0020] In addition, one embodiment involves the pulse sequence,following detection of an interference signal, not being transmittedagain until after transmission of the pulse sequence dependent on thetransmission signal has ended, or when, if there are a plurality ofchannels, transmission has ended on all channels.

[0021] If just one transmission channel is available for carrying outthe inventive transmission method, then interference signal detectionneeds to be interrupted when the pulse sequence is transmitted so as notto detect the pulse sequence resulting from the transmission signalincorrectly as an interference signal.

[0022] In order to be able to perform interference signal detection on apermanent basis, one embodiment of the invention provides for a firstand a second transmission channel to be provided, with a first pulsesequence, which comprises at least one pulse, being generated asstipulated by the transmission signal and being transmitted via thefirst channel, and with a second pulse sequence, which comprises atleast one pulse, being generated with a time stagger with respect to thefirst pulse sequence and being transmitted via the second channel. Sincethe first and second pulse sequences are generated with a time staggerwith respect to one another, it is ensured that it is always possible tomonitor one of the two channels for the occurrence of interferencesignals, with the information obtained from this monitoring being ableto be used for repeating pulse sequences on both channels. In thiscontext, use is made of the insight that interference signals normallyinfluence both channels to the same extent, which means thatinterference identified on the channel on which no pulse sequence iscurrently being transmitted can be used for the other channel in orderto repeat the pulse sequence currently being transmitted when theinterference arises. In this embodiment, the first pulse sequence isthus transmitted again following an interference signal detected on thefirst and/or second channel, and the second pulse sequence istransmitted again following an interference signal detected on thesecond and/or first channel.

[0023] In another embodiment, provision is made for interference signaldetection not to be performed on one of the transmission channels, butrather for a separate sensor to be used for this purpose which can bedesigned in the manner of a transmission channel which is actually notused for transmitting useful signals.

[0024] The inventive method can be used for any transmission signalswhich can stipulate that a pulse sequence comprising at least one pulsebe generated.

[0025] The transmission signal can be, by way of example, a bivalentsignal which has a first or a second signal level and is used as acontrol signal for a load arranged at the receiver end of the channel.In the case of such bivalent signals, the fundamental information isheld in the change of signal level, as is known, which means thattransmission of the information requires only transmission of a suitablepulse after such a change of signal level.

[0026] In one embodiment of the method, in which only one transmissionchannel is provided, a change in the signal level of the transmissionsignal from the first signal level to the second signal level, forexample, entails a pulse which is positive with respect to areference-ground potential being generated and transmitted, and a changein the signal level of the transmission signal from the second signallevel to the first signal level entails a pulse which is negative withrespect to a reference-ground potential being generated and transmitted.If an interference signal is detected on the channel between thesepulses, then the respective pulse is repeated, provided that the levelof the transmission signal has not changed in the interim.

[0027] The method can naturally also be used for pulse-code-modulatedtransmission methods, in which pulse sequences with more than one pulseeach are generated on the basis of a transmission signal. Thus, a changein the signal level of the transmission signal from the first to thesecond level entails a first pulse sequence, which comprises a pluralityof pulses, being generated and transmitted, and a change in the signallevel of the transmission signal from the second to the first levelentails a second pulse sequence, which comprises a plurality of pulses,being generated and transmitted, the first and second pulse sequencesbeing different. A respective one of these two pulse sequences istransmitted again following detection of an interference signal on thechannel.

[0028] In one embodiment of the method, in which a first transmissionchannel and a second transmission channel are available, a change in thesignal level of the transmission signal from the first signal level tothe second signal level entails the first pulse sequence, whichcomprises at least one pulse, being generated and being transmitted viathe first channel, and a change in the signal level of the transmissionsignal from the second signal level to the first signal level entailsthe second pulse sequence, which comprises at least one pulse, beinggenerated and being transmitted by the second channel. The first andsecond pulse sequences can in this case match in terms of their form,that is to say in terms of the number of pulses and the progression overtime.

[0029] The at least one pulse sequence, which, in line with theinventive method, is transmitted again following detection of aninterference signal, can naturally be dependent on the plurality oftransmission signals and can comprise almost any number of pulses,provided that the duration of the pulse sequence is shorter than theinterval of time at which level changes occur in the transmission signalwhich is to be transmitted.

[0030] The method according to the invention is particularly suitablefor transmission via a channel that has an inductive coupling element ora transformer, particularly a coreless transformer.

[0031] With the above and other objects in view there is also provided,in accordance with the invention, a transmission apparatus, comprising:

[0032] an input terminal for receiving at least one transmission signal,and at least one output terminal to be coupled to a transmissionchannel;

[0033] at least one pulse-generating circuit connected between saidinput terminal and said output terminal, said pulse-generating circuithaving at least one actuating input and generating a pulse sequence withat least one pulse as stipulated by the transmission signal; and

[0034] an interference signal detection circuit connected to saidpulse-generating circuit, said interference signal detection circuitproviding an actuating signal causing the pulse-generating circuit togenerate the pulse sequence again as stipulated by the actuating signal.

[0035] In other words, the novel transmission apparatus has an inputterminal for supplying at least one transmission signal, and at leastone output terminal which can be coupled to a transmission channel, withthe input terminal and the output terminal having at least onepulse-generating circuit, having an actuating input, connected betweenthem which generates a pulse sequence having at least one pulse asstipulated by the transmission signal. The output terminal of thetransmission apparatus and the actuating input on the pulse-generatingcircuit have an interference signal detection circuit connected betweenthem which provides an actuating signal for the pulse-generatingcircuit, with the pulse-generating circuit generating the pulse sequenceagain as stipulated by the actuating signal.

[0036] In one embodiment, the interference signal detection circuit inthe transmission apparatus comprises a detector circuit, connected tothe output terminal of the transmission apparatus, and anactuating-signal-generating circuit, connected downstream of thedetector circuit. The detector circuit connected to the channel monitorsthe channel for the occurrence of interference signals and provides anoutput signal, on the basis of which the actuating-signal-generatingcircuit provides the actuating signal.

[0037] Preferably, the actuating-signal-generating circuit additionallygenerates the actuating signal on the basis of the at least one pulsesequence which is generated by the pulse-generating circuit and istransmitted to the channel, in order to ensure that no repetition of thepulse sequence is started during a period of time in which a pulsesequence is currently being output to the channel.

[0038] It is also possible to disable the detector circuit forinterference signal detection during the period of time in which a pulsesequence is being output to the channel, in order to prevent the pulsesequence which results from the transmission signal and is beingtransmitted for the first time or again from being incorrectly detectedas an interference signal. Instead of the detector circuit, it is alsopossible to disable the actuating signal generating circuit duringtransmission of a useful pulse, in order to prevent, during transmissionof a useful pulse sequence, the useful pulse sequence itself from beingtaken as grounds for repeated transmission.

[0039] A transmission apparatus in line with one embodiment of theinvention comprises a first output terminal, which can be coupled to afirst channel, and a second output terminal, which can be coupled to asecond channel, with the input terminal and the first output terminalhaving a first pulse-generating circuit connected between them, and theinput terminal and the second output terminal having a secondpulse-generating circuit connected between them. In this case, the firstoutput terminal and the control input on the first pulse-generatingcircuit have a first interference signal detection circuit, whichprovides a first actuating signal, connected between them, and thesecond output terminal and the control input on the secondpulse-generating circuit have a second interference signal detectioncircuit, which provides a second actuating signal, connected betweenthem.

[0040] In this transmission apparatus, which is suitable fortransmission via two channels, one of the two channels is always beingmonitored for the occurrence of interference signals, with the firstpulse-generating circuit providing the first pulse sequence again asstipulated by the first actuating signal, that is to say on the basis ofdetection of an interference signal on the first channel, and asstipulated by the second actuating signal, that is to say on the basisof detection of an interference signal on the second channel, andoutputting it to the channel. Preferably, the second pulse-generatingcircuit also provides the second pulse sequence again as stipulated bythe second actuating signal and as stipulated by the first actuatingsignal, and outputs it to the channel.

[0041] In addition, in one embodiment of the inventive transmissionapparatus, the first interference signal detection circuit generates thefirst actuating signal as stipulated by the second status signal, thisstatus signal indicating whether a second pulse sequence is currentlybeing transmitted via the second channel, so that it is possible toensure that the first pulse sequence is not transmitted again untilsignal transmission has also ended on the second channel. In addition,the second interference signal detection circuit generates the secondactuating signal as stipulated by a first status signal, which indicateswhether a first pulse sequence is currently being transmitted to thefirst channel.

[0042] In one embodiment of the inventive transmission apparatus, the atleast one pulse-generating circuit generates the pulse sequence after aprescribed edge of the input signal and repeats the pulse sequencepreferably after a prescribed edge of the actuating signal and at aprescribed level of the input signal.

[0043] Other features which are considered as characteristic for theinvention are set forth in the appended claims.

[0044] Although the invention is illustrated and described herein asembodied in a method and transmission apparatus for transmitting abivalent signal, it is nevertheless not intended to be limited to thedetails shown, since various modifications and structural changes may bemade therein without departing from the spirit of the invention andwithin the scope and range of equivalents of the claims.

[0045] The construction and method of operation of the invention,however, together with additional objects and advantages thereof will bebest understood from the following description of specific embodimentswhen read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0046]FIG. 1 is a block diagram of a transmission system for datatransmission via a channel that contains a potential barrier;

[0047]FIG. 2 plots exemplary signal profiles for a transmission signal(Sin), for a pulse sequence (PS) and for a signal (KS) detected on afirst channel in a first embodiment of an inventive method;

[0048]FIG. 3 plots exemplary signal profiles for a transmission signal(Sin), for a pulse sequence (PS1) which is to be transmitted via achannel and for a signal (KS) detected on the channel in a furtherembodiment of the inventive method;

[0049]FIG. 4 is a block diagram of a transmission system for datatransmission via a first and a second channel which each contain apotential barrier;

[0050]FIG. 5 plots exemplary signal profiles for a transmission signal(Sin), for a first pulse sequence (PS1) which is to be transmitted via afirst channel, for a second pulse sequence (PS2) which is to betransmitted via a second channel, for a signal (KS1) detected on thefirst channel and for a signal (KS2) detected on the second channel in asecond embodiment of the method according to the invention;

[0051]FIG. 6 is a schematic block diagram of a novel transmissionapparatus for carrying out a method as shown in FIG. 2;

[0052]FIG. 7 shows exemplary time profiles for some of the signalsarising in the transmission apparatus shown in FIG. 6;

[0053]FIG. 8 is a schematic block diagram of a first pulse-generatingcircuit and a first interference signal detection circuit in atransmission apparatus for carrying out a method as shown in FIG. 5;

[0054]FIG. 9 is a schematic block diagram of a second pulse-generatingcircuit and a second interference signal detection circuit in atransmission apparatus for carrying out a method as shown in FIG. 5;

[0055]FIG. 10 is a block diagram of an exemplary embodiment of amonoflop as shown in FIGS. 8 and 9;

[0056]FIG. 11 shows exemplary time profiles for some of the signalsarising in the pulse-generating circuit and in the interference signaldetection circuit shown in FIG. 8;

[0057]FIG. 12 is a schematic block diagram of a further exemplaryembodiment of a transmission apparatus; and

[0058]FIG. 13 is a diagram of an exemplary embodiment of a receiverapparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0059] Referring now to the figures of the drawing in detail and first,particularly, to FIG. 1 thereof, there is shown a transmission systemfor transmitting a transmission signal Sin via a channel which, in theexemplary embodiment, has a transformer 3. In the exemplary embodiment,the transformer comprises two inductively coupled coils or windingswhich are connected to different reference-ground potentials GND1, GND2.The transmission system comprises a transmission apparatus 1 to whichthe transmission signal Sin is supplied and which outputs a signal,particularly a pulse sequence PS, to the channel. The receiver end ofthe channel has a receiver 2 which generates, from a signal received viathe channel, an output signal Sout that matches the transmission signalSin when the channel is free of interference.

[0060] On the transmitter-end section of the channel, it is possible todetect a signal KS present on the channel, this signal KS being able tobe dependent both on a pulse sequence which is dependent on thetransmission signal Sin and on an interference signal which is injectedinto the channel externally. This signal KS present on the channel isfed back to the transmission apparatus K1 in order to be able to detectinterference signals on the channel, as will be explained below.

[0061] A first exemplary embodiment of an inventive method fortransmitting a transmission signal Sin via a channel is explained belowwith reference to example time profiles for a transmission signal Sin,for a pulse sequence PS which is generated by the transmission apparatus10 on the basis of the transmission signal Sin and is output to thechannel, and for a channel signal KS which can be detected on thechannel.

[0062] The transmission signal Sin shown in FIG. 2 is a bivalenttransmission signal which alternately assumes a first signal level P1and a second signal level P2. This transmission signal to be transmittedvia the channel is, by way of example, a control signal for a load (notshown in more detail) arranged at the receiver end and is used forturning on or turning off this load, for example.

[0063] On the basis of this bivalent transmission signal Sin, theinventive method shown in FIG. 2 involves a pulse sequence beinggenerated which has a positive pulse when the signal level of thetransmission signal Sin rises from the first level P1 to the secondlevel P2, that is to say when there is a rising edge of thistransmission signal Sin, as is the case at times t1 and t5 in FIG. 2.Upon every rising edge of the transmission signal Sin, a pulse sequencecomprising a positive pulse is therefore generated. These pulsesgenerated in the transmission apparatus shown in FIG. 1 bring about acorresponding detectable signal pulse on the channel, with this signalpulse RS which can be detected on the channel possibly appearing with adelay with respect to the pulse in the pulse signal PS or appearingsmooth, depending on the channel properties, although this is not takeninto account in the illustration shown in FIG. 2.

[0064] At time t2, an interference pulse, in the example a negativeinterference pulse, appears on the channel in the signal profile shownin FIG. 2. This interference pulse is detected and, when theinterference pulse has subsided, the pulse transmitted at time t1 isrepeated. This corrects misinformation at the receiver end. This isbecause the receiver cannot distinguish whether a pulse on the channelresults from a signal which is output by the transmission apparatus orfrom an interference pulse. If the receiver is designed to put a loadinto a particular operating state when a negative pulse is received viathe channel, then the negative interference pulse appearing at time t2could bring about this actuation of the load. The correct pulse, whichis repeated after the interference pulse has subsided and is dependenton the transmission signal Sin, ensures that the load is put back intothe correct operating state if an incorrect state change has occurred onaccount of the interference pulse. The positive pulse is transmittedagain immediately after the interference pulse has subsided or with aslight time delay after the interference pulse has subsided.

[0065] In the exemplary embodiment shown in FIG. 2, a negative pulse istransmitted when the level of the transmission signal Sin falls from thesecond level P2 to the first level, that is to say upon every fallingedge of the transmission signal Sin, as shown at a time t3.Correspondingly, this negative pulse is transmitted again when aninterference pulse or interference signal starting at time t4 hassubsided, in order to avoid or to correct misactuation of the load as aresult of the interference signal.

[0066] The transmission method illustrated in FIG. 2 involves the use ofjust one transmission channel for the data transmission, with thischannel being used to transmit a positive pulse upon every rising edgeof the transmission signal Sin and to transmit a negative pulse uponevery falling edge of the transmission signal Sin, and the positivepulse being repeated following detection of an interference pulse on thechannel for as long as the transmission signal Sin maintains its levelafter a rising edge, and the negative pulse being repeated followingdetection of an interference pulse on the channel for as long as thetransmission signal Sin maintains its level after a falling edge. If thetransmission signal changes its state during interference, then a pulseor a correction pulse is transmitted, when the interference hassubsided, which is associated with the new level of the transmissionsignal.

[0067]FIG. 3 illustrates an inventive method in which the transmissionsignal Sin is transmitted in pulse-code-modulated form, with a risingedge of the transmission signal Sin being converted into a first pulsesequence PS1 with two pulses, the interval of time between these twopulses being T1, by way of example. A falling edge of the transmissionsignal Sin is converted into a second pulse sequence PS2, with theinterval of time between these pulses being T2, for example.

[0068] The duration of the pulse sequences PS1, PS2 is normally shorterthan the duration for which the transmission signal Sin assumes thesecond signal level P2 or the first signal level P1 at consecutivetimes. In the case of the method shown in FIG. 3, detection of aninterference pulse is followed by the first pulse sequence PS1 beingrepeated if the transmission signal Sin continues to be at the secondsignal level P2. Correspondingly, the second pulse sequence PS2 isrepeated after an interference pulse has been detected on the channel,if the transmission signal Sin has the first signal level P1. If thetransmission signal Sin has changed its level in the interim—during theoccurrence of an interference signal—then, when the interference hassubsided, a signal sequence is transmitted which is associated with thepresent level or state of the transmission signal Sin.

[0069] To give a better understanding of a further embodiment of aninventive method and of an inventive transmission apparatus, FIG. 4illustrates a data transmission system for transmitting the transmissionsignal Sin via two separate channels, each of the channels having atransformer 31, 32 as a potential barrier. Connected to the two channelsat the receiver end is a receiver circuit 21 which provides an outputsignal Sout on the basis of signals present on the channels, thereceiver circuit 21 and a transmission apparatus 10 arranged at thetransmitter end being matched to one another such that the output signalSout matches the transmission signal Sin if the channel is free ofinterference. The transmission apparatus 10 is supplied with thetransmission signal Sin, with the transmission apparatus comprising afirst transmission apparatus 11 which generates a first pulse sequencePS1 on the basis of the transmission signal Sin and outputs it to thefirst channel, and the transmission apparatus 10 having a secondtransmission apparatus 12 which generates a second pulse sequence PS2 onthe basis of the transmission signal Sin and outputs it to the secondchannel.

[0070] In addition, the first transmission apparatus 11 monitors thefirst channel, to which end the first transmission apparatus 11 issupplied with a signal KS1 which can be detected on the first channel.The second transmission apparatus monitors the second channel, with thesecond transmission apparatus 12 being supplied with a channel signalKS2 which can be detected on the channel. Preferably, the first andsecond transmission apparatuses are coupled to one another, as shown inFIG. 4. As a result of this, upon detection of an interference pulse onthe first channel, the pulse sequence provided by the secondtransmission apparatus 12 can be transmitted again on the basis of afirst refresh signal or actuating signal SRE1 generated by the firsttransmission apparatus 11, and the first pulse sequence provided by thefirst transmission apparatus 11 can be transmitted again to the firstchannel on the basis of a second refresh signal or actuating signal SRE2which is provided by the second signal generating apparatus 12 and isdependent on detection of an interference pulse on the second channel.The pulse sequences PS1, PS2 generated by the first and secondtransmission apparatuses 11, 12 are preferably transmitted at staggeredtimes.

[0071] While a pulse sequence resulting from the transmission signal Sinis being transmitted via one of the channels, this channel is disabledfor detection of an interference pulse, in order to prevent a usefulsignal pulse from being incorrectly detected as an interference pulse.Since the first and second pulse sequences PS1, PS2 are generated andtransmitted at staggered times, however, one of the two channels isalways available for interference signal detection, with use being madeof the insight that interference signals normally influence bothchannels at the same time.

[0072]FIG. 5 illustrates an inventive signal transmission method usingtwo transmission channels, with example time profiles for thetransmission signal Sin, for the first pulse sequence PS1, for thesecond pulse sequence PS2, for a signal KS1 present on the first channeland for a signal KS2 present on the second channel being shown below oneanother in FIG. 5.

[0073] In the case of the method shown in FIG. 5, upon every rising edgeof the bivalent transmission signal Sin a pulse is generated by thefirst transmission apparatus 11 and is output to the first channel, asshown at times t1 and t7. This transmission pulse is transmitted againvia the associated channel when an interference signal has been detectedon one of the two channels. In the case of the time profile shown inFIG. 5, transmission of the pulse on the first channel is accompanied bythe appearance of an interference pulse, which in the example isnegative with respect to the pulse which is transmitted. Thisinterference pulse corrupts the signal transmitted via the firstchannel, as shown using the profile for the signal KS1. The shape of theinterference pulse becomes clear with reference to the time profile forthe signal KS2. In the case of the inventive method, during the periodof time during which a pulse is being transmitted via one of the twochannels, no interference signal detection is carried out on thischannel.

[0074] In the case of the example shown in FIG. 5, upon every fallingedge of the transmission signal Sin a pulse is transmitted via thesecond channel, as shown at time t4 in FIG. 5. Pulses via the firstchannel and via the second channel are therefore transmitted atstaggered times, which means that the second channel is used forinterference signal detection during transmission of pulses via thefirst channel. Correspondingly, following detection of an interferencepulse in the signal KS2 which is tapped off on the second channel, thepulse generated after the rising edge at time t1 is repeated at time t2after the interference pulse has subsided. Although an interferencepulse has appeared on both channels during transmission of the firstpulse and has resulted in incorrect transmission of the first pulse,this error is corrected using the second channel, which is usedexclusively for interference signal detection during transmission of apulse via the first channel.

[0075] Following the transmission of a pulse, the first channel is alsoused for interference signal detection, so that the pulse transmittedvia the first channel is also repeated when an interference signal isdetected exclusively on the first channel, as shown from time t3 onward.When the interference pulse has subsided, the pulse resulting from thepositive edge of the transmission signal Sin is transmitted again.

[0076] Correspondingly, during transmission of a pulse or of a pulsesequence which is dependent on the transmission signal Sin via thesecond channel, the first channel is used exclusively for interferencesignal detection, which means that the pulse transmitted via the secondchannel is also transmitted again if an interference signal greatlyinterferes with the second channel during transmission of the pulse. Inthis context, it is assumed that interference pulses normally concernboth channels at the same time. When a pulse or a pulse sequence hasbeen transmitted via the second channel, the second channel is also usedfor interference signal detection, which means that the pulsetransmitted via the second channel is also repeated if an interferencesignal is detected only on the second channel. In FIG. 5, such aninterference pulse starts at time t6, by way of example. The pulseresulting from the falling edge of the transmission signal Sin is inthis case transmitted again after this interference pulse has subsided.

[0077] It goes without saying that, in connection with the embodiment ofthe inventive method in which pulse sequences are transmitted via twomutually isolated channels, it is possible to use any pulse sequenceswhich are dependent on the transmission signal Sin and, followingdetection of an interference signal or interference pulse on at leastone of the two channels, are transmitted again via the associatedchannel.

[0078] In one modification of the method illustrated in FIG. 5, thefirst pulse generated after a level change in the transmission signalSin or the first pulse sequence generated is delayed if, together withthis level change, an interference signal or an interference pulse isdetected on one of the two channels, and the first pulse or the firstpulse sequence is not transmitted until after this interference signalhas subsided.

[0079]FIG. 6 shows a detailed view of an exemplary embodiment of aninventive transmission apparatus as shown in FIG. 1 for carrying out amethod as shown in FIG. 2 at the transmitter end.

[0080] The transmission apparatus comprises an input terminal forsupplying the transmission signal Sin and is coupled to the channel bymeans of an output terminal, only one of the windings on the channel'stransformer being shown in FIG. 6 for reasons of clarity.

[0081] The transmission apparatus comprises a driver circuit DRV havingtwo transistors T1, T2 whose load paths are connected in series betweena positive supply potential Vcc and a negative supply potential Vss,with a node which is common to the two transistors being connected tothe channel. The potential on the channel can be pulled to positivepotential or to negative potential using this driver circuit DRV, thepotential on the channel being positive when the first transistor T1connected to the positive supply potential Vcc is on and the secondtransistor T2 connected to the negative supply potential Vss is off.Correspondingly, the potential on the channel is negative when thesecond transistor is on and the first transistor T2 is off. The firsttransistor T1 is in the form of a bipolar transistor in the exemplaryembodiment, while the second transistor T2 is a MOSFET. To provideactuating signals for the two transistors T1, T2, a pulse-generatingcircuit 110 is provided which provides a first pulse sequence PSH foractuating the first transistor T1 and a second pulse sequence PSL foractuating the second transistor T2. To convert the logic levels of thesetwo pulse sequences PSH, PSL to suitable potentials for actuating thetwo transistors T1, T2, these pulse sequences are supplied to drivercircuits DT1 and DT2, respectively, the driver circuit DT1 beingconnected to the control connection on the first transistor T1, and thedriver circuit DT2 being connected to the control connection on thesecond transistor T2.

[0082] To provide the pulse sequences PSH, PSL, the pulse-generatingcircuit 110 comprises a number of logic components which are explainedbelow.

[0083] The pulse sequence PSH for actuating the first transistor T1 isavailable at the output of a first NOR gate NO1, and the pulse sequencePSL for actuating the second transistor T2 is available on a second NORgate NO2. The first NOR gate NO1 is supplied with an output signal froman upstream NAND gate NA1, with the output signal from the first NANDgate NA1 delayed by means of a delay element DL1 and inverted by meansof a Schmitt trigger ST1, and with a turn-on signal PON.Correspondingly, the second NOR gate NO2 is supplied with the outputsignal from a second NAND gate NA2, with the output signal from thisNAND gate NA2 delayed by means of a delay element DL2 and inverted bymeans of a Schmitt trigger, and with the turn-on signal PON.

[0084] The first NAND gate NA1 is supplied with the transmission signalSin and with an actuating signal or refresh signal SRE. This actuatingsignal SRE normally has the level of a logic 1, provided that nointerference pulse is detected on the channel, as will be explainedbelow. The second NAND gate NA2 is supplied with the transmission signalSin inverted by means of an inverter IN1 and likewise with the actuatingsignal SRE.

[0085] The way in which this pulse-generating circuit 110 works isexplained briefly below, with reference being made to the time profilefor the pulse sequences PSH, PS7 in FIG. 7, in which the turn-on signalPON, the transmission signal Sin, the pulse sequence PSH and the pulsesequence PSL are shown below one another in the top part.

[0086] It will first be assumed that the actuating signal SRE has thelevel of a logic 1 and that in addition the turn-on signal PON, which islow-active, has the level of a logic 0. If the turn-on signal Sinlikewise assumes the level of a logic 0 or the lower signal level P1,then the output of the NAND gate NA1 produces the level of a logic 1,which, together with the level of the turn-on signal PON via the NORgate NO1, gives the level of a logic 0 at the output of the NOR gateNO1. The output of the second NOR gate NO2 likewise produces the levelof a logic 0 where the input signal Sin has the level of a logic 0. Inthis case, the output of the NAND gate NA2 produces the level of a logic0. The delay element DL2 is designed to pass on level changes from alogic 0 to a logic 1 without a delay and to pass on level changes from alogic 1 to a logic 0 with a delay time of τ1. Assuming that the lowlevel at the output of the NAND gate NA2 has already been produced forlonger than this delay time τ1, the output of the inverting Schmitttrigger ST2 produces a high level, which means that the output of theNOR gate NO2 produces a low level.

[0087] If the input signal Sin changes from the low level (logic 0) tothe high level (logic 1), then the level at the output of the first NANDgate NA1 changes from a logic 1 to a logic 0. Like the delay elementDL2, the delay element DL1 is designed to pass on level changes fromlogic 1 to logic 0 with a delay time of τ1 and to pass on level changesfrom logic 0 to logic 1 without a delay. The output of the invertingSchmitt trigger ST1 following the change in the level of the outputsignal from the NAND gate NA1 thus continues to produce a low level fora period τ1, which means that the output of the NOR gate NO1 following achange in the level of the transmission signal Sin from low to highproduces a pulse for a period τ1, as shown in FIG. 7 on the rising edgeof the transmission signal Sin. Correspondingly, the output of the NORgate NO2 following a falling edge of the transmission signal Sinproduces a pulse of duration τ1 for a period τ2.

[0088] Upon every rising edge of the transmission signal Sin, the firsttransistor T1 turns on by virtue of the pulse in the pulse sequence PSH,in order to draw the channel to a positive potential, as becomes clearfrom the channel signal KS which can be tapped off on the channel andwhose time profile is shown at the bottom in FIG. 7. If the firsttransistor T1 is subsequently off, the output of the driver circuit DRVis at high impedance. The driver circuit DRV is a “tristate drivercircuit” which can assume three states, a first state, in which thefirst transistor T1 is on and the second transistor T2 is off, whichmeans that the output of the driver circuit DRV produces a positivesupply potential Vcc, a second state, in which the second transistor T2is on and the first transistor T1 is off, which means that the output ofthe driver circuit DRV produces a negative potential Vss, and a thirdstate, in which both transistors T1, T2 are off, which means that theoutput of the driver circuit DRV is at high impedance.

[0089] A pulse of the signal PSL turns on the second transistor T2, as aresult of which the channel is drawn to negative potential, as likewisebecomes clear from the channel signal KS which can be tapped off on thechannel.

[0090] In general, the first path in the pulse-generating circuit 110,containing the first NAND gate NA1, the delay element DL1 and theSchmitt trigger ST1 and also the NOR gate NO1, generates a pulse ofduration τ1 when one of the two input signals on the NAND gate NA1 risesfrom the level of a logic 0 to the level of a logic 1, while the otherof the two input signals maintains the level of a logic 1.Correspondingly, the second path in the pulse-generating circuit 110,containing the second NAND gate NA2, the delay element DL2, the Schmitttrigger ST2 and the NOR gate NO1, generates a pulse of duration τ1 whenone of the two input signals on the NAND gate NA2 changes from the levelof a logic 0 to the level of a logic 1, while the other of the two inputsignals maintains the level of a logic 1. The first path in thepulse-generating circuit 110 thus also generates a pulse of duration τ1when the input signal Sin assumes the level of a logic 1 and the refreshsignal SRE rises from a low level to a high level. Correspondingly, thesecond path generates a pulse of duration τ1 for actuating the secondtransistor T2 when the input signal Sin assumes the value of a logic 0and the refresh signal SRE rises from the value of a logic 0 to thevalue of a logic 1.

[0091] This refresh signal or actuating signal is generated by anactuating-signal-generating circuit 100 as stipulated by an interferencesignal detection signal provided by a detector circuit DET, the refreshsignal SRE falling to a low level for a period τ2 following detection ofan interference signal so as subsequently to rise to a high level and toprompt fresh generation of a pulse by the pulse-generating circuit 110,as explained below.

[0092] The detector circuit DET is coupled to the channel and has acomparator arrangement, with a first comparator K1 and a secondcomparator K2, which is used to compare the channel signal with apositive reference value Vref and with a negative value −Vref. Outputsignals F1, F2 from these comparators K1, K2 are supplied to a NOR gateNO3, these two output signals F1, F2 assuming the value of a logic 0 foras long as the channel signal K1 is within a range prescribed by thereference values −Vref and Vref. The interference signal detectionsignal EMI is then accordingly at the value of the level of a logic 1.If the magnitude of the channel signal KS exceeds one of these tworeference values, then one of the comparator output signals F1 or F2 ishigh, while the other is low, which means that the interference signaldetection signal EMI assumes the value of a logic 0, as is likewiseillustrated in FIG. 7, where the comparator output signals F1, F2 areillustrated together in the timing diagram in this case.

[0093] In the detector circuit DET, it is not possible to distinguish inthe example whether the rise or fall in the channel signal KS to a valuewhich is outside of the range is brought about by an interference signalor one of the transistors T1, T2 turned on by the pulses PSH, PSL, whichmeans that the interference detection signal EMI also assumes the valueof a logic low level for a useful signal pulse. To prevent such a usefulpulse from being detected as an interference signal, the actuatingsignal SRE is generated in the actuating-signal-generating circuit onthe basis of an enable signal FS which is dependent on the pulsesequences PSH, PSL. This enable signal FS is supplied to a NAND gate NA3whose output produces the actuating signal SRE. The NAND gate NA3 isalso supplied with the interference signal detection signal EMI directlyand with the interference signal detection signal EMI delayed by meansof a delay element DL4 and inverted by means of a Schmitt trigger ST4.The delay element DL4 is designed to pass on level changes in theinterference signal detection signal EMI from a low level to a highlevel delayed by a delay time τ2, while level changes from a high levelto a low level are passed on without any delay. If the level of theinterference signal detection signal EMI thus changes from a low levelto a high level when an interference signal or else a useful signal hassubsided, then this level change is passed on only with a delay, whichmeans that the interference signal detection signal EMI and the signalproduced at the output of the Schmitt trigger SD4 do not differ for aperiod τ2 after this level change, with both assuming the value of alogic 1.

[0094] If the enable signal FS also has the value of a logic 1 duringthis period, then the actuating signal SRE falls to the level of thelogic 0 for this period τ2 so as to prompt generation of a refresh pulseof duration τ1 in the manner described above when subsequently rising toa logic 1.

[0095] Regardless of a level change in the interference signal detectionsignal EMI, the actuating signal SRE maintains the level of a logic 1when the enable signal FS assumes the level of a logic 0. The enablesignal FS is generated by means of a logic arrangement which has a NORgate NO4, a delay element DL3 connected downstream of the NOR gate NO4,a Schmitt trigger ST3 connected downstream of the delay element DL3, andan inverter IN2 connected downstream of the Schmitt trigger ST3, withthe enable signal FS being produced at the output of the inverter IN2.The NOR gate NO4 is supplied with the pulse sequences PSH, PSL. Thedelay element DL3 is designed to pass on level changes at the output ofthe NOR gate NO4 from low to high delayed by a delay time τ3. Everypulse in the pulse sequences PSH, PSL causes this logic circuit toprompt a low level for the enable signal FS for a period τ1+τ3 in orderto disable the NAND gate NA3 during this period and thus to prevent auseful pulse from being followed by generation of a corresponding lowpulse for the actuating signal and by the useful pulse being transmittedagain.

[0096] A low pulse for the actuating signal, which stipulates that thepulse-generating circuit 110 can generate a pulse again and output it tothe channel, can thus be generated only when no useful pulse iscurrently being transmitted via the channel, this being ensured for thetransmission apparatus shown in FIG. 6 by virtue of the NAND gate at theoutput of the actuating-signal-generating circuit being disabled for theperiod τ1+τ3 after the start of the pulse PSH or PSL. Although thedetector circuit detects a potential change on the channel during thisperiod, the detected potential change is not used to generate a lowpulse for the actuating signal, since the actuating-signal-generatingcircuit 100 is disabled.

[0097] Instead of the actuating-signal-generating circuit 100, it isalso possible to disable the detector circuit DET in order to prevent auseful pulse from being detected as an interference signal duringtransmission of this useful pulse.

[0098] FIGS. 8 to 11 are subsequently used to illustrate a transmissionapparatus 10 for carrying out an inventive transmission method as shownin FIG. 5. FIG. 8 shows a block diagram of the first transmissionapparatus 11 shown in FIG. 4, and FIG. 9 shows a block diagram of thetransmission apparatus 12 shown in FIG. 4.

[0099] The two transmission apparatuses 11, 12 are of identical designand differ only in that the transmission apparatus 11 is supplied withthe input signal Sin directly, and the transmission apparatus 12 issupplied with the input signal Sin inverted by means of an inverterIN31. To illustrate the identical design of the transmission apparatuses11 and 12, the references for corresponding components and correspondingsignals in the illustrations shown in FIGS. 8 and 9 differ only in theirlast digit, the references for components and signals associated withthe first transmission apparatus 11 ending in the digit 1 and thereferences for components and signals associated with the secondtransmission apparatus 12 ending in the digit 2.

[0100] The first transmission apparatus 11 has an output terminal K31providing the first actuating signal SRE1, which is supplied to aconnection terminal K42 on the second transmission apparatus 12.Correspondingly, the second transmission apparatus has an outputterminal K32 providing the second actuating signal SRE2, which issupplied to a connection terminal K41 on the first transmissionapparatus 11.

[0101] Besides the actuating signals SRE1, SRE2, which are also shown inFIG. 4, the two transmission apparatuses 11, 12 respectively deliver astatus signal S1 or S2. A first status signal S1 from the firsttransmission apparatus is available on a first output terminal K11 andis supplied to an input terminal K22 on the second transmissionapparatus 12. Correspondingly, the second transmission apparatus 12provides a second status signal 32 on an output terminal K12, and thisstatus signal is supplied to an input terminal K21 on the firsttransmission apparatus 11.

[0102] On account of the identical design of the two transmissionapparatuses, the description below is limited to describing thetransmission apparatus 11 in FIG. 8. Time profiles for selected signalsshown in the transmission apparatus 11 in FIG. 8 are illustrated in FIG.11 to give a better understanding of the manner of operation.

[0103] The transmission apparatus 11 comprises a NAND gate NA11 which issupplied with the transmission signal Sin, with the first actuatingsignal SRE1 generated in the first transmission apparatus 11, and withthe second actuating signal SRE2 generated in the second transmissionapparatus 12. As will be explained, the two actuating signals SRE1, SRE2are generated such that they assume the value of a logic 1 if nointerference signal is detected on one of the two channels, and theyfall to a low level for a prescribed period when an interference signalhas been detected. In the absence of interference, the output of theNAND gate NA11 produces an output signal SNA11 with a logic high levelif the input signal Sin has the level of a logic 0. The output signalfrom the NAND gate NA11 is supplied to the clock input of a downstreamD-type flipflop DF11, the D-input of this flipflop being at a positivelogic potential V1. The noninverting output QP of this flipflop DF11produces the first pulse sequence PS1, which is output via a drivercircuit DRV1 to the channel, of which only the transformer 31 is shownin FIG. 8. By way of example, the driver circuit DRV1 is a conventionalinverter which applies the channel to a positive supply potential Vcc orreference-ground potential GND as stipulated by the pulse sequence PS1.It is not necessary to transmit a negative pulse during datatransmission via two channels.

[0104] If the input signal Sin changes from a low level to a high level,then the output signal SNA11 from the NAND gate NA11 accordingly changesto a low level, as illustrated in FIG. 11. Upon the falling edge of thegate signal SNA11, the D-type flipflop DF11 assumes the value of thelogic potential V1, as a result of which the level at the noninvertingoutput of the flipflop DF11 rises to the value of a logic 1, which meansthat a positive potential is applied to the channel via the driver DRV1.

[0105] A signal KS1 present on the channel is supplied to an invertingSchmitt trigger ST11, whose output signal SST11 is supplied via a NANDgate NA21 to the reset input R of the D-type flipflop DF11. If thesignal KS1 rises above a threshold value prescribed by the Schmitttrigger ST11, then the output signal SST11 from the Schmitt trigger ST11assumes a low level and resets the flipflop DF11 via the NAND gate NA21,as a result of which the level at the flipflop's noninverting output QPfalls to a low level. When the high pulse produced at the output QP ofthe flipflop is generated, use is made of the fact that, particularlyduring signal transmission via a channel which contains an inductivetransformer, the potential on the channel follows the pulse PS1 onlyafter a time delay, which means that the D-type flipflop DF11 is notreset until after this delay time, which determines the duration of thepulse. The duration of the pulse after a rising edge of the input signalSin is thus prescribed by the channel properties and possibly by thedelay times of the logic components. In this way, the pulse length ofthe transmission pulse PS1 and hence the poser consumption areautomatically minimized. Delay times for the logic components areincidentally taken into account in the illustration shown in FIG. 1 onlywhere they are necessary for the operation of the circuit arrangement.

[0106] The NAND gate NA11, the flipflop DF11, the Schmitt trigger ST11and the NAND gate NA21 together form a pulse-generating circuit 111which generates a pulse PS1 at the noninverting output of the D-typeflipflop DF11, and outputs it to the channel via the driver DRV1,whenever one of the input signals on the NAND gate NA11, that is to saythe transmission signal Sin or one of the two actuating signals SRE1,SRE2, rises from a low level to a high level, provided that the othertwo signals have a high level. In this case, the duration of the pulsegenerated is always the same and is dependent on the properties of thechannel and on the delay times of the logic gates used.

[0107] The transmission apparatus 12 shown in FIG. 9 has a correspondingpulse-generating circuit 112 which comprises the inverter IN32, the NANDgate NA12, the flipflop DF12, the Schmitt trigger ST12 and the NAND gateNA22. In line with the manner of operation of the pulse-generatingcircuit shown in FIG. 8, this pulse-generating circuit 112 generates apulse PS2 when the transmission signal Sin, which is inverted by theinverter IN32, falls from a high level to a low level, provided that theactuating signals SRE1, SRE2 have a high level. In addition, thetransmission apparatus shown in FIG. 9 generates a pulse PS2 wheneverthe transmission signal Sin has a logic low level and the level of oneof the two actuating signals SRE1, SRE2 changes from a low level to ahigh level.

[0108] The transmission apparatus 11 shown in FIG. 8 also comprises aninterference signal detection circuit having a detector circuit DET1 andan actuating-signal-generating circuit 101, which provides the firstactuating signal SRE1. The design of the detector circuit DET1 can beequivalent to the design of the detector circuit DET shown in FIG. 6,with the reference potentials being suitably chosen on the basis of thepotential conditions on the channel such that any signals on thechannel, be they useful signals or interference signals, can bedetected. Whether a potential change detected on the channel is theresult of a useful signal or of an interference signal is decided in theactuating-signal-generating circuit 101. The detector circuit DET1delivers an interference signal detection signal EMI1 which assumes thevalue of a logic 0 if the channel signal K11 assumes a value outside ofa range prescribed by the reference potentials used in the detectorcircuit. Regardless of whether the channel signal KS1 is situatedoutside of this range as a result of a useful pulse or as a result of aninterference pulse, the interference signal detection signal or channeldetection signal EMI1 assumes the value of a logic 0.

[0109] The interference signal detection signal EMI1 is supplied to theclock input CLK on a further D-type flipflop DF21, whose D-input is atthe positive logic potential V1. This flipflop DF21 takes on the logicpotential V1 upon the falling edge of the interference signal detectionsignal EMI1, which means that the noninverting output QP produces thevalue of a logic 1. The interference signal detection signal EMI and theoutput signal from the flipflop DF21 are supplied to a NAND gate NA51.The output signal from this NAND gate NA51 remains at the level of alogic 1 for as long as the output signal from the flipflop DF21 and theinterference signal detection signal EMI1 differ, that is to say for aslong as a signal is detected on the channel. If the interference signaldetection signal EMI1 rises, after this signal present on the channelhas subsided, to the value of a logic 1, then the output signal from theNAND gate SNA51 assumes the value of a logic 0, as illustrated in FIG.11.

[0110] The output signal SNA51 from the NAND gate NA51 is supplied to aNOR gate NO11 together with the status signal S2 from the secondtransmission apparatus 12. This status signal S2, which is generated onthe basis of the status signal S1 (yet to be explained) from thetransmission apparatus 11, assumes the level of a logic 0 if no datatransmission is taking place via the second channel. In this case, whenthe signal detected on the channel ends, that is to say when theinterference signal detection signal EMI1 rises to the value of a logic1, the output signal SNO11 from the NOR gate NO11 changes to the levelof a logic 1, as illustrated in FIG. 11.

[0111] The output signal SNO11 from the NOR gate NO11 is supplied to amonoflop MF1, whose design corresponds to that shown in FIG. 10, forexample. This monoflop comprises a NAND gate NA60, to which the signalSNO11 is supplied first directly and secondly delayed by means of adelay element DL60 and inverted by means of an inverter IN60. Themonoflop MF1 thus generates, upon every rising edge of the output signalSNO11, an actuating signal SRE1 which assumes the level of a logic 0upon every falling edge of the signal SNO11 for a period τ.

[0112] When the actuating signal SRE1 falls to the level of the logic 0,the output signal from the NAND gate NA11 rises to the level of a logic1, and upon the next falling edge of this signal SNA11 after the delaytime τ the level at the noninverting output QP of the flipflop DF11again rises to a high level in order to generate a repeated pulse whichis output to the channel via the driver DRV1.

[0113] As explained, the interference signal detection signal does notdistinguish between interference signal and useful signal on thechannel. To prevent a useful pulse transmitted via the channel, whichuseful pulse is also detected by the detection circuit DET1, from beingincorrectly interpreted as an interference pulse and resulting in thegeneration of a low pulse for the actuating signal SRE1, and hence inpulse repetition, the example is provided with an RS flipflop RS1 whosereset input R is connected to the noninverting output of the flipflopDF11 and whose set input is connected to the output of the Schmitttrigger ST11. The noninverting output of the flipflop RS1 is connectedto the reset input of the D-type flipflop DF21 via a NAND gate NA41. Theflipflop RS1 is reset upon every rising edge of the pulse sequence PS1and resets the D-type flipflop DF21 via the NAND gate NA41, so that alow level, resulting from transmission of the useful pulse, of theinterference signal detection signal EMI1 cannot change the level of theactuating signal SRE1. The RS-type flipflop RS1 and hence the D-typeflipflop DF21 remain reset until the Schmitt trigger ST11 sets theflipflop RS1 and resets the D-type flipflop DF11. Only when pulsetransmission via the first channel has ended can a potential change,detected by the detector circuit DET1, on the channel bring about achange to the signal level of the actuating signal SRE1 in order toresult in fresh pulse generation.

[0114] The NAND gate NA41 is supplied not only with the output signalfrom the flipflop RS1 but also with the actuating signal SRE1, as aresult of which the D-type flipflop DF21 is reset whenever a low pulseis generated for the actuating signal SRE1, in order to start freshinterference signal detection.

[0115] The inventive transmission apparatus 11 generates a low pulse forthe actuating signal SRE1, resulting in repetition of the pulse PS1,whenever a potential change is detected on the channel, potentialchanges during transmission of a useful pulse being masked out, so thatthey cannot result in a low pulse being generated for the actuatingsignal SRE1.

[0116] The output of the RS-type flipflop RS1 is also connected to aninverter IN21 whose output provides the status signal S1. This statussignal S1 assumes a high level for as long as the flipflop RS1 is set,that is to say for as long as a useful pulse is being transmitted. Thestatus signal S2 in the second transmission apparatus 12 is generated ina corresponding manner and assumes the value of a logic 1 for as long asa useful pulse is being transmitted by means of the second transmissionapparatus.

[0117] As already explained above, the status signal S2 prevents a lowpulse from being generated for the actuating signal SRE1 for as long asit assumes the value of a logic 1. Since the first actuating signal SRE1prompts both repetition of a useful pulse on the first channel andrepetition of a useful pulse on the second channel, the status signal S2generated by the second transmission apparatus ensures that no low levelis generated for the first actuating signal SRE1 during the period inwhich pulse transmission is currently taking place on the secondchannel, in order thus to prevent a refresh pulse from being generatedat the same time as a useful pulse is being transmitted. The low pulsefor the actuating signal SRE1 is not generated until after the statussignal S2 has assumed a low level again, that is to say after datatransmission on the second channel has ended.

[0118] Since the pulse sequences PS1, PS2 are generated with a timestagger in the case of the transmission apparatus shown in FIGS. 8 and9, one of the two channels is always available for interference signaldetection, with an interference pulse detected on one of the twochannels not resulting in repetition of the useful pulse on the other ofthe two channels until useful pulse transmission has ended on this otherone of the two channels.

[0119] The output signal SST11 from the Schmitt trigger ST11 is suppliedto the reset input R on the D-type flipflop DF11 via a NAND gate NA21,the other input of this gate NA21 being supplied with the output signalfrom a further NAND gate NA31, whose input signals supplied are thesignal produced at the inverting output of the flipflop DF11 and theinterference signal detection signal EMI1 inverted by means of aninverter IN11. This arrangement containing the inverter IN11 and thegates NA21, NA31 “disables” the flipflop DF11 while an interferencesignal is present by virtue of the flipflop remaining permanently reset,and thereby prevents useful signals from being output to the channelduring interference. The useful signal is thus not generated, triggeredby a low pulse in the signal SRE1, and transmitted to the channel untilafter the interference has subsided.

[0120] In the case of the transmission apparatuses shown in FIGS. 8 and9, the useful information to be transmitted is held in a respectivepulse which is generated and transmitted via a first or second channelon the basis of the transmission signal. This pulse is transmitted againfollowing detection of an interference signal on the channel. It isnaturally also possible for a modified pulse-generating circuit (notshown in more detail) to generate and transmit longer pulse sequences onthe basis of one or more transmission signals, this pulse sequencelikewise being transmitted again upon detection of an interferencesignal.

[0121] For the exemplary embodiments illustrated up to now, it isassumed that the channels are used both for signal transmission and forinterference signal detection. In another embodiment, interferencesignal detection is carried out by providing a sensor which is usedexclusively for interference signal detection and not for useful signaltransmission. FIG. 12 shows an exemplary embodiment of a transmissionapparatus for carrying out such a method. This transmission apparatus isa modification of the apparatus shown in FIG. 6 and differs therefrom inthat interference signal detection is carried out by providing a sensorSEN to which the detection circuit DET instead of the channel isconnected. The detection circuit evaluates a sensor signal SES in themanner explained above for the channel signal KS, in order thereby toprompt transmission of a correction pulse when an interference pulse isdetected.

[0122] The sensor SEN is produced adjacently to the transmission channeland is designed such that corresponding interference signals are broughtabout in it as in the channel in the case of externally appliedinterference. In the simplest case, the sensor comprises a line whichruns parallel to the transmission channel and may also contain atransformer, in order to simulate the transmission channel as accuratelyas possible using the sensor SEN.

[0123] Interference signal detection using the sensor SEN can be used asan alternative or in addition to the interference signal detection onthe transmission channel. Thus, by way of example, a transitionapparatus as shown in FIG. 8, which monitors interference on thetransmission channel, can be complemented by the use of a sensorarrangement for ascertaining interference signals on the channel whichsupplies a further actuating signal (not shown in more detail) to theNAND gate NA11.

[0124] In the case of interference signal detection, be it on thetransmission channel or on the sensor, it is not possible to ascertainthe cause of the interference on the channel.

[0125] In the case of one embodiment of the inventive method, provisionis therefore made for “interference” or “interference pulses” to beinjected into the channel at the receiver end at regular or irregularintervals of time or upon triggering by particular events, so as toprovoke repeated transmission of a transmission pulse. The receiver isthen always able to request the present transmission pulse or the stateof the transmission signal, unless externally caused interferencearises.

[0126]FIG. 13 shows an exemplary embodiment of a suitable receiverapparatus 2 which is connected to the channel. The receiver apparatuscomprises a receiver 201 which is connected to the channel and convertsthe signals detected on the channel into the output signal. In addition,the receiver apparatus comprises a driver circuit 202 which is connectedto the channel and emits quasi interference signals to the channel inorder to provoke repetition of the transmission pulse or of thetransmission pulse sequence at the transmitter end. By way of example,the driver circuit is a tristate driver circuit after the fashion of thedriver circuit DRV in FIG. 6 or 12. The receiver 201 and the drivercircuit 202 are coupled to one another, as a result of which thereceiver is able to trigger the emission of a quasi interference pulseS202 if, by way of example, a received signal Sout′ cannot beunambiguously converted into the signal Sout. In addition, the driver202 disables the receiver when a quasi interference pulse is emitted sothat such a pulse cannot be incorrectly received as a useful pulse.

[0127] The provocation of fresh transmission of a useful pulse or of auseful pulse sequence works particularly in the case of channels whichcontain a transformer, since transformers are bidirectional components,which means that the signals generated at the receiver end aretransmitted to the transmitter and are detected there as interferencesignals, which triggers fresh transmission of the useful signal.

I claim:
 1. A method for transmitting information contained in atransmission signal via at least one channel, the method which comprisesthe following steps, to be performed at a transmitter end: generating atleast one pulse sequence with at least one pulse as stipulated by thetransmission signal; outputting the pulse sequence to the at least onechannel; monitoring the channel for a presence of an interferencesignal; and repeating the pulse sequence if an interference signal isdetected on the channel.
 2. The method according to claim 1, whichcomprises: generating a first pulse sequence comprising at least onepulse as stipulated by the transmission signal and transmitting thefirst pulse sequence via a first channel; generating a second pulsesequence comprising at least one pulse with a time offset relative tothe first pulse sequence and transmitting the second pulse sequence viaa second channel; if an interference signal is detected on one of thefirst and second channels, retransmitting the first pulse sequence; andif an interference signal is detected on one of the second and firstchannels, retransmitting the second pulse sequence.
 3. The methodaccording to claim 1, which comprises, upon detecting an interferencesignal, transmitting the at least one pulse sequence only after nofurther interference signal is detected.
 4. The method according toclaim 1, which comprises, if an interference signal is detected prior toa first transmission of the pulse sequence, holding off transmitting thepulse sequence until after no further interference signal is detected.5. The method according to claim 1, wherein the transmission signal is abivalent signal having a first signal level or a second signal level,and the at least one pulse sequence comprises a pulse produced after achange in the signal level.
 6. The method according to claim 5, whereina change in the signal level of the transmission signal from the firstsignal level to the second signal level involves a positive pulse of thepulse sequence with respect to a reference potential, and a change inthe signal level of the transmission signal from the second signal levelto the first signal level involves a negative pulse of the pulsesequence with respect to the reference potential.
 7. The methodaccording to claim 5, which comprises: when the signal level of thetransmission signal changes from the first signal level to the secondsignal level, generating the first pulse sequence with at least onepulse and transmitting the first pulse sequence via the first channel;and when the signal level of the transmission signal changes from thesecond signal level to the first signal level, generating the secondpulse sequence with at least one pulse and transmitting the second pulsesequence via the second channel.
 8. The method according to claim 1,wherein the transmission signal has a first signal level or a secondsignal level, and the method comprises: when the signal level of thetransmission signal changes from the first signal level to the secondsignal level, generating a first pulse sequence with a plurality ofpulses; when the signal level of the transmission signal changes fromthe second signal level to the first signal level, generating a secondpulse sequence having a plurality of pulses and differing from the firstpulse sequence; and commonly transmitting the first and second pulsesequences via a common channel.
 9. The method according to claim 1,which comprises producing the at least one pulse sequence in dependenceon a plurality of transmission signals.
 10. The method according toclaim 1, which comprises monitoring the channel with a sensor disposedadjacent the channel.
 11. The method according to claim 1, which furthercomprises injecting at least one pulse into the channel at a receiverend, detecting the pulse as an interference signal, and therebytriggering a repetition of the pulse sequence.
 12. The method accordingto claim 1, wherein the transmitting step comprises transmitting thetransmission signal via a channel containing a potential barrier. 13.The method according to claim 1, wherein the transmitting step comprisestransmitting the transmission signal via a channel containing a magneticcoupling element forming a potential barrier.
 14. A transmissionapparatus, comprising: an input terminal for receiving at least onetransmission signal, and at least one output terminal to be coupled to atransmission channel; at least one pulse-generating circuit connectedbetween said input terminal and said output terminal, saidpulse-generating circuit having at least one actuating input andgenerating a pulse sequence with at least one pulse as stipulated by thetransmission signal; and an interference signal detection circuitconnected to said pulse-generating circuit, said interference signaldetection circuit providing an actuating signal causing thepulse-generating circuit to generate the pulse sequence again asstipulated by the actuating signal.
 15. The transmission apparatusaccording to claim 14, wherein said interference signal detectioncircuit is connected between said output terminal of the transmissionapparatus and said actuating input of said pulse-generating circuit. 16.The transmission apparatus according to claim 14, which comprises asensor disposed adjacent the transmission channel, and wherein saidinterference signal detection circuit is connected between said sensorand said actuating input of said pulse-generating circuit.
 17. Thetransmission apparatus according to claim 14, wherein said interferencesignal detection circuit has a detector circuit, connected to saidoutput terminal of the transmission apparatus, and anactuating-signal-generating circuit, connected downstream of saiddetector circuit, in a signal flow direction, saidactuating-signal-generating circuit providing the actuating signal independence on an output signal from said detector circuit.
 18. Thetransmission apparatus according to claim 17, wherein saidactuating-signal-generating circuit is configured to also generate theactuating signal in dependence on the at least one pulse sequence. 19.The transmission apparatus according to claim 14, wherein: said at leastone output terminal is one of two output terminals including a firstoutput terminal, for coupling to a first channel, and a second outputterminal, for coupling to a second channel; said input terminal and saidfirst output terminal having a first pulse-generating circuit connectedtherebetween, and said input terminal and said second output terminalhaving a second pulse-generating circuit connected therebetween; saidfirst output terminal and a control input of said first pulse-generatingcircuit having a first interference signal detection circuit forproviding a first actuating signal connected therebetween; and saidsecond output terminal and a control input of said secondpulse-generating circuit having a second interference signal detectioncircuit for providing a second actuating signal connected therebetween.20. The transmission apparatus according to claim 19, wherein at leastone of the following is true: said first pulse-generating circuit isconfigured to provide the pulse sequence again as stipulated by thefirst actuating signal and as stipulated by the second actuating signal;and said second pulse-generating circuit is configured to provide thepulse sequence again as stipulated by the second actuating signal and asstipulated by the first actuating signal.
 21. The transmission apparatusaccording to claim 20, wherein at least one of the following is true:said first interference signal detection circuit is configured togenerate the first actuating signal as stipulated by a second statussignal indicating whether or not a second pulse sequence is beingtransmitted to the second channel; and said second interference signaldetection circuit is configured to generate the second actuating signalas stipulated by a first status signal indicating whether or not a firstpulse sequence is being transmitted to the first channel.
 22. Thetransmission apparatus according to claim 14, wherein said at least onepulse-generating circuit is configured to generate the pulse sequenceafter a prescribed edge of the input signal.
 23. The transmissionapparatus according to claim 14, wherein said at least onepulse-generating circuit is configured to repeat the pulse sequenceafter a prescribed edge of the actuating signal and at a prescribedlevel of the input signal.
 24. A signal transmission assembly,comprising: a transmission apparatus according to claim 14; and areceiver apparatus having a receiver coupled to the channel and a drivercoupled to the channel and configured to output signals to the channelto be detected in said transmission apparatus as interference signals.